package com.zues.thread.aqs;

import com.zues.thread.util.ThreadUtil;
import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * @ClassName Demo1
 * @Description TODO
 * @Author zeus
 * @Date 3/24/2025 5:05 PM
 * @Version 1.0
 **/
@Slf4j(topic = "c.Demo1")
public class Demo1 {

    public static void main(String[] args) {
        MyLock myLock = new MyLock();

        new Thread(()->{
            myLock.lock();
            try {
                log.debug("locking...");
                ThreadUtil.sleep(1);
            }finally {
                log.debug("unlocking...");
                myLock.unlock();
            }
        },"t1").start();


        new Thread(()->{
            myLock.lock();
            try {
                log.debug("locking...");
            }finally {
                log.debug("unlocking...");
                myLock.unlock();
            }
        },"t2").start();
    }

}

/**
 * 自定义锁（不可重入锁）
 */
class MyLock implements Lock {

    //独占锁 同步器类
    class MySync extends AbstractQueuedSynchronizer {

        //尝试获得锁
        @Override
        protected boolean tryAcquire(int arg) {
            if (compareAndSetState(0, 1)) {
                //加上了锁,并设置 owner为当前线程
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        //尝试释放锁
        @Override
        protected boolean tryRelease(int arg) {
            setExclusiveOwnerThread(null);
            //设置volatile变量在后面，防止重排序
            setState(0);
            return true;
        }

        //是否持有独占锁
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        public Condition newCondition() {
            return new ConditionObject();
        }
    }

    private MySync sync = new MySync();

    //加锁 不成功会加入等待队列
    @Override
    public void lock() {
        sync.acquire(1);
    }

    //加锁 可打断
    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    //尝试加锁 只会尝试1次，不成功返回false
    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    //尝试加锁 超时机制
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1, unit.toNanos(time));
    }

    //解锁
    @Override
    public void unlock() {
        sync.release(1);
    }

    //创建条件变量
    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }
}